(1) Field of the Invention
This invention relates to the treatment of aqueous or other liquid sludges and more particularly to a process and system for clarifying a liquid medium containing solid particulate matter by separating the solid constituents comprising the sludge from the aqueous or other liquid medium to thereby clarify the water or other liquid. The invention has utility in the continuous treatment of a liquid containing solid particulate matter, where the liquid to be treated enters the system continuously or from a collection vessel and solids are separated and removed and the stream is clarified so that it can be discharged into municipal sewers or adjacent rivers and streams.
(2) Description of the Prior Art
Sludge results from sewage treatment processes, is produced in municipal water purification facilities and is found as a by-product of almost all industrial, chemical and commercial operations. In many continuous processes, and in some batch operations, the sludge is pumped as a mixture of solids in water and other liquid chemicals into a storage vessel, such as a tank, concrete pit, or the like. In the storage vessel the sludge, which has a moisture content of from about 90% to 98% is allowed to stand.
The heavier components of the sludge gradually settle to the bottom of the tank or vessel and it is a common practice to use a floating pump to remove as much of the water as possible. Alternatively, baffles may be employed in the settling vessel with an overflow pipe located opposite the feed pipe. When the vessel has reached its capacity and the maximum amount of aqueous sludge-containing medium has been decanted, the remaining sludge is removed by a combination of mechanical and manual means. Present techniques require workers to enter the vessels to manipulate the equipment or to actually shovel the heavy solids during cleaning operations.
The further handling and disposal of this sludge with its high water content can present a serious problem. Methods such as drying in open beds, flash and spray drying require large investments in land and/or capital, and any drying system operating at high temperature may be prohibitively expensive to operate unless waste heat is available from other sources.
Another option for disposing of accumulated sludge is simply to contract with a third-party to carry the material away in drums, tankers or the like. Such services are likewise becoming costly as available disposal sites diminish and as governmental regulations on treatment and disposal become more stringent.
A further problem exists with respect to the decanted liquid, which is seldom clear enough to re-use or to be discharged into the municipal sewer or nearby river without further treatment. Most governmental units have established regulations regarding the chemical composition, and the physical size of solid particulate matter which can be discharged into municipal sewer systems or returned to natural streams and rivers. In other cases the liquid may be a solvent which must be disposed of safely.
It is therefore a purpose of this invention to provide a system and process for the treatment of solid-containing liquid effluents to effect a complete clarification of the liquid medium.
It is also a purpose of this invention to provide a system and process capable of clarification of a liquid medium which has either a continuous or discontinuous flow.
Another purpose of this invention is to provide a system and process for use in the cleaning of settling, or decantation tanks to effect the removal of sludge and solid particulate matter which does not require a worker to enter the tank or vessel.
It is also an important purpose of this invention to provide a unitary, integrated system and process for the treatment of an aqueous medium containing solid matter which combines the separation of heavy particles with extra fine filtration, at either a constant or a discontinuous flow, to effect the complete removal of solid particulate matter greater than about 1 micron contained in the water to thereby permit the collection or recycling of clarified and if desired substantially pure water.
It is a further goal of this invention to provide a completely automated process and system for cleaning the interior of sludge settling tanks without human intervention, and to provide for removal of the sludge and solid particulate matter, as well as fine filtration, which permits direct discharge into the sewer of clarified, and if desired, chemically neutralized aqueous effluent.
Another objective of the invention to provide for a system and process as described above which can be fixed or mobile without limitation as to the continuous or discontinuous nature of the flow of the liquid stream to be treated.
It is also an object of the invention to provide a continuous process and system for the treatment of chemical and industrial wastes comprising solids and non-aqueous liquid solvents, such as organic solvents, in which the solid particulate matter having a diameter of one micron and larger are removed and collected, and the liquid solvent medium is clarified and collected for further use.